1. Field of the Invention
The present invention relates to voltage-controlled bidirectional vertical components and more specifically to voltage-controlled bidirectional vertical switches for medium-power applications enabling, for example, switching of loads connected to the mains, such as electro-domestic appliances.
2. Discussion of the Related Art
FIG. 1 is a very simplified cross-section view of a voltage-controlled vertical bidirectional switch formed from two vertical transistors of IGBT type (isolated gate bipolar transistor). It should be clear, as usual in the representation of semiconductor components, that the drawing is not to scale.
Switch 10 includes two vertical IGBT transistors 11A, 11B. Each transistor is comprised of a lightly-doped N-type substrate 13A, 13B delimited by a P-type isolating wall 14A, 14B. The lower surface of substrate 13A, 13B is uniformly coated with a P-type layer 15A, 15B.
On the upper surface side of substrate 13A, 13B is arranged a cell network 16A, 16B. For clarity, only two cells 16A, 16B are shown for each transistor 11A, 11B. Each cell 16A, 16B is comprised of a well 17A, 17B including a heavily-doped P-type central region 18A, 18B and a more lightly doped P-type peripheral region. A heavily-doped N-type ring 19A, 19B is formed in well 17A, 17B. The portion of well 17A, 17B outside of ring 19A, 19B is covered with an isolated gate 20A, 20B. Each transistor 11A, 11B also includes a P-type ring 21A, 21B, which surrounds cell network 16A, 16B. A peripheral heavily-doped N-type channel stop ring 22A, 22B is located at the periphery of transistor 11A, 11B.
A cathode metallization M1A, M1B contacts central region 18A, 18B of well 17A, 17B and N-type ring 19A, 19B of each cell 16A, 16B, as well as P-type ring 21A, 21B. An anode metallization M2A, M2B covers P-type layer 15A, 15B. A metal ring M3A, M3B is connected to peripheral channel stop ring 22A, 22B to make it equipotential. Similarly, a metal ring M4A, M4B is connected to isolating wall 14A, 14B to make it equipotential.
The terminals associated with isolated gates 20A, 20B of each transistor 11A, 11B are respectively designated with references G1, G2.
The lower surface of transistor 11A, located on the left-hand side of FIG. 1, directly rests on a radiator 23. The lower surface of transistor 11B, located to the right of FIG. 1, rests on radiator 23 with an interposed insulator 24.
The vertical bidirectional switch is obtained by connecting the two vertical IGBT transistors 11A, 11B as follows. Metallization M1A of transistor 11A, located to the left of FIG. 1, is connected by an electric connector 28 to the anode, formed by metallization M2B, of transistor 11B located to the right of FIG. 1. The cathode formed by metallization M1B of this latter transistor 11B is connected by an electric connector 29 to radiator 23. The two IGBT transistors 11A, 11B are thus connected in antiparallel. The main terminals of bidirectional switch 10 correspond to radiator 23 and to metallization M1A. According to the voltages on gates G1, G2, one or the other of the two transistors, or none of them, can be turned on. A voltage-controlled bidirectional switch is thus obtained.
The above voltage-controlled bidirectional switch has the disadvantage of not being monolithic. Conversely, it includes two transistors formed on separate chips. It thus has a relatively significant bulk and requires use of wirings to connect the two transistors. Further, one of the transistors is laid on the radiator via an insulator. It is often difficult to obtain an insulator both ensuring a good electric insulation between the transistor and the radiator and a satisfactory heat exchange between the two elements.
The present invention aims at monolithically forming a voltage-controlled bidirectional switch.
To achieve this and other objects, the present invention provides a vertical voltage-controlled bidirectional monolithic switch formed between the upper and lower surfaces of a semiconductor substrate surrounded with a peripheral wall, including a first multiple-cell vertical IGBT transistor extending between a cathode formed on the upper surface side and an anode formed on the lower surface side; and a second multiple-cell vertical IGBT transistor extending between a cathode formed on the lower surface side and an anode formed on the upper surface side, in which the cells of each transistor are arranged so that portions of the cells of a transistor are active upon operation of the other transistor.
The present invention also provides a vertical voltage-controlled bidirectional monolithic switch formed in a substrate of a first conductivity type surrounded with a peripheral wall of a second conductivity type, including a network of upper cells, formed on the upper surface side of the substrate, each upper cell being formed of a ring of the first conductivity type formed in a well of a second conductivity type, the well region outside of the ring forming a channel ring covered with an upper isolated gate; an upper metallization, forming a first main electrode, connected to the central region of the well and to the ring of each upper cell; a network of lower cells similar to the upper cells, formed on the lower surface side of the substrate, opposite to the network of upper cells; and a lower metallization forming a second main electrode, connected to the central region of the well and to the ring of each lower cell.
According to an embodiment of the present invention, the lower isolated gate is connected to a sink which crosses a region of the substrate from the lower surface to the upper surface, the sink being connected to a gate contact formed on the upper surface side.
According to an embodiment of the present invention, the lower isolated gate is connected to the sink by a metallization isolated from the lower metallization.
According to an embodiment of the present invention, the lower metallization covers the entire lower surface.
According to an embodiment of the present invention, the lower metallization is connected to the peripheral wall.
According to an embodiment of the present invention, the substrate region crossed by the sink is isolated from the substrate regions where the networks of upper and lower cells are formed by the peripheral wall which extends in an auxiliary wall of the second conductivity type.
According to an embodiment of the present invention, the peripheral wall extends on the lower surface side in a lower ring of the second conductivity type surrounding the network of lower cells.
According to an embodiment of the present invention, on the upper surface side, an upper ring of the second conductivity type surrounds the network of upper cells and is connected to the upper metallization.
According to an embodiment of the present invention, on the upper surface side, a heavily-doped channel stop ring of the first conductivity type surrounds the upper ring of the second conductivity type.
The foregoing objects, features and advantages of the present invention, will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.